Tools and methods for use in completion of a wellbore

ABSTRACT

A ported tubular is provided for use in casing a wellbore, to permit selective access to the adjacent formation during completion operations. A system and method for completing a wellbore using the ported tubular are also provided. Ports within the wellbore casing may be opened, isolated, or otherwise accessed to deliver treatment to the formation through the ports. A tool assembly and method for completing a well are also provided. The tool includes debris relief features that enable use in solids-laden environments, for example in the presence of sand. Forward and reverse circulation pathways to the isolated interval are present to allow clearing of debris from the wellbore annulus while the sealing device remains set against the wellbore.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 15/187,507 filed Jun. 20, 2016, which is a continuation of U.S. application Ser. No. 14/317,975 filed Jun. 27, 2014 now issued as U.S. Pat. No. 9,745,826, which is a division of U.S. application Ser. No. 13/100,796 filed May 4, 2011 now issued as U.S. Pat. No. 8,794,331, which claims the benefit of U.S. provisional application No. 61/394,077 filed on Oct. 18, 2010, the disclosures of which are hereby incorporated by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates generally to oil, gas, and coal bed methane well completions. More particularly, methods and tool assemblies are provided for use in accessing, opening, or creating one or more fluid treatment ports within a downhole tubular, for application of treatment fluid therethrough. Multiple treatments may be selectively applied to the formation through such ports along the tubular, and new perforations may be created as needed, in a single trip downhole. The present invention also relates to a tool string for use in stimulating multiple intervals of a wellbore in the presence of flowable solids, such as sand.

2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98

Various tools and methods for use downhole in the completion of a wellbore have been previously described. For example, perforation devices are commonly deployed downhole on wireline, slickline, cable, or on tubing string, and sealing devices such as bridge plugs, packers, and straddle packers are commonly used to isolate portions of the wellbore for fluid treatment.

In vertical wells, downhole tubulars may include ported sleeves through which treatment fluids and other materials may be delivered to the formation. Typically, these sleeves are run in the casing, tubing string, or production liner string, and are isolated using external casing packers straddling the sleeve. Such ports may be mechanically opened using any number of methods including: using a shifting tool deployed on wireline or jointed pipe to force a sleeve open mechanically; pumping a ball down to a seat to shift the sleeve open; applying fluid pressure to an isolated segment of the wellbore to open a port; sending acoustic or other signals from surface, etc. These mechanisms for opening a port or shifting a sliding sleeve are not always reliable, and are not intended for use with coiled tubing.

Recently, tool assemblies for performing multiple functions in a single trip downhole have been developed, greatly reducing the cost of well completion operations. For example, CA 2,397,460 describes a bottom hole assembly for use in the sequential perforation and treatment of multiple wellbore intervals in a single trip downhole. Perforation with an explosive charge followed by sealing of the wellbore and application of treatment to the wellbore annulus is described. No active debris relief is described to maintain tool functionality in the presence of debris/solids, such as sand. Accordingly, the use of this tool in the presence of flowable solids would be associated with significant risk of debris-related tool malfunction, jamming or immobility of the tool assembly, and potential loss of the well if the tool assembly cannot be retrieved.

The use of jet nozzles in cleaning cased wellbores, and fracturing uncased wellbores, has been previously described in detail. Notably, CA 2,621,572 describes the deployment of a fluid jetting device above an inflatable packer. This type of packer provides minimal sealing against the uncased wellbore, allowing the assembly to travel up or downhole while the packers are inflated. This system is not suitable for use in perforation of a cased wellbore or in debris-laden environments, due in part to the imperfect seal provided by the inflatable packers, and the inability to clear solids that may settle over the packer and/or may block the jet nozzles.

Use of any sealing device in the presence of significant amounts of sand or other solids increases the risk of tool malfunction. Further, the tool may be lost downhole should a solids blockage occur during treatment, or when the formation expels solids upon release of hydraulic pressure in the wellbore annulus when treatment is complete. Moreover, when jetting abrasive fluid to perforate a wellbore casing, the prior art does not provide a suitable method for delivering clear fluid to the perforations/removing settled solids from the perforations in the event of a solids blockage. Typical completion assemblies have many moving components for actuating various downhole functions, and the presence of sand or other solids within these actuation mechanisms would risk jamming these mechanisms, causing a malfunction or permanent damage to the tool or well. Correcting such a situation is costly, and poses significant delays in the completion of the well. Accordingly, well operators, fracturing companies, and tool suppliers/service providers are typically very cautious in their use of sand and other flowable solids downhole. The addition of further components to the assembly adds further risk of solids blockages in tool actuation, and during travel of the tool from one segment of the wellbore to another, further risking damage to the assembly. Increasing the number of segments to be perforated and treated in a single trip also typically increases the size of the assembly, as additional perforating charges are required. Excessive assembly lengths become cumbersome to deploy, and increase the difficulty in removal of the assembly from the wellbore in the presence of flowable solids.

BRIEF SUMMARY OF THE INVENTION

In one aspect, there is provided a method for delivering treatment fluid to a formation intersected by a wellbore, the method comprising the steps of: lining the wellbore with tubing, the liner comprising one or more ported tubular segments, each ported tubular segment having one or more lateral openings for communication of fluid through the liner to a formation adjacent the wellbore; deploying a tool assembly downhole on tubing string, the tool assembly comprising an abrasive fluid perforation device and a sealing member; locating the tool assembly at a depth generally corresponding to one of the ported tubular segments; setting the sealing member against the liner below the ported tubular segment; and delivering treatment fluid to the ported tubular segment.

In an embodiment, the lateral openings are perforations created in the liner. In another embodiment, the openings are ports machined into the tubular segment prior to lining the wellbore.

In an embodiment, the sealing member is a straddle isolation device comprising first and second sealing members, and the tool assembly further comprises a treatment aperture between the first and second sealing members, the treatment aperture continuous with the tubing string for delivery of treatment fluid from the tubing string to the formation through the ports. For example, the first and/or second sealing members may be inflatable sealing elements, compressible sealing elements, cup seals, or other sealing members.

In another embodiment, the sealing member is a mechanical set packer, inflatable packer, or bridge plug.

In another embodiment, the ported tubular segment comprises a closure over one or more of the lateral openings, and the method further comprises the step of removing a closure from one or more of the lateral openings. The closure may comprise a sleeve slidingly disposed within the tubular segment, and the method may further comprise the step of sliding the sleeve to open one or more of the lateral openings.

In further embodiments, the step of sliding the sleeve comprises application of hydraulic pressure and/or mechanical force to the sleeve.

In an embodiment, the tubing string is coiled tubing.

In an embodiment of any of the aforementioned aspects and embodiments, the method further comprises the step of jetting one or more new perforations in the liner. The step of jetting one or more new perforations in the liner may comprise delivering abrasive fluid through the tubing string to jet nozzles within the tool assembly.

The method may further comprise the step of closing an equalization valve in the tool assembly to provide a dead leg for monitoring of bottom hole pressure during treatment.

In a second aspect, there is provided a method for shifting a sliding sleeve in a wellbore, comprising: providing a wellbore lined with tubing, the tubing comprising a sleeve slidably disposed within a tubular, the tubular having an inner profile for use in locating said sleeve; providing a tool assembly comprising: a locator engageable with said locatable inner profile of the tubular; and a resettable anchor member; deploying the tool assembly within the wellbore on coiled tubing; engaging the inner profile with the locator; setting the anchor within the wellbore to engage the sliding sleeve; applying a downward force to the coiled tubing to slide the sleeve with respect to the tubular.

In an embodiment, the step of setting the anchor comprises application of a radially outward force with the anchor to the sleeve so as to frictionally engage the sleeve with the anchor. The sleeve may comprise an inner surface of uniform diameter along its length, free of any engagement profile. The inner surface may be of a diameter consistent with the inner diameter of the tubing.

In an embodiment, the tool assembly further comprises a sealing member associated with the anchor, and wherein the method further comprises the step of setting the sealing member across the sleeve to provide a hydraulic seal across the sleeve.

In an embodiment, the step of applying a downward force comprises application of hydraulic pressure to the wellbore annulus.

In a third aspect, there is provided a method for shifting a sliding sleeve in a wellbore, comprising: providing a wellbore lined with tubing, the tubing comprising a sleeve slidably disposed within a tubular, the tubular having an inner profile for use in locating said sleeve; providing a tool assembly comprising: a locator engageable with said locatable inner profile of the tubular; and a resettable sealing member; deploying the tool assembly within the wellbore on coiled tubing; engaging the inner profile with the locator; setting the sealing member across the sliding sleeve; applying a downward force to the coiled tubing to slide the sleeve with respect to the tubular.

In an embodiment, the step of setting the sealing member comprises application of a radially outward force with the sealing member to the sleeve so as to frictionally engage the sleeve with the sealing member.

In an embodiment, the sleeve comprises an inner surface of uniform diameter along its length, free of any profile. The inner diameter may be consistent with the inner diameter of the tubing.

In a fourth aspect, there is provided a method for shifting a sliding sleeve in a deviated wellbore, comprising: providing a deviated wellbore having a sleeve slidably disposed therein; providing a work string for use in engaging the sleeve, the work string comprising: tubing string; a sealing element operatively attached to the tubing string; and sleeve location means operatively associated with the sealing element; deploying said work string within the wellbore to position the sealing element proximal to said sleeve; setting the sealing element across the wellbore to engage the sleeve; applying a downward force to the sealing element to shift the sliding sleeve

In an embodiment, the step of applying a downward force comprises applying hydraulic pressure to the wellbore annulus.

In a fifth aspect, there is provided a ported tubular for installation within a wellbore to provide selective access to the adjacent formation, the ported tubular comprising: a tubular housing comprising one or more lateral fluid flow ports, the housing adapted for installation within a wellbore; a port closure sleeve disposed against the tubular housing and slidable with respect to the housing to open and close the ports; and, location means for use in positioning a shifting tool within the housing below the port closure sleeve.

In an embodiment, the location means comprises a profiled surface along the innermost surface of the housing or sleeve, the profiled surface for engaging a location device carried on a shifting tool deployable on tubing string. The sleeve may have an inner surface of uniform diameter along its length, free of any engagement profile. The inner diameter may be consistent with the inner diameter of tubular segments adjacent the ported tubular segment.

In another aspect, there is provided a ported tubular for installation within a wellbore to provide selective access to the adjacent formation, the ported tubular comprising: a tubular housing comprising one or more lateral fluid flow ports, the housing adapted for installation within a wellbore; a port closure sleeve disposed against the tubular housing and slidable with respect to the housing to open and close the ports; means for locking the slidable position of the sleeve with respect to the housing.

In an embodiment, the means for locking comprises engageable profiles along adjacent surfaces of the sleeve and housing.

In another aspect, there is provided an assembly for deployment within a wellbore, the assembly comprising: a perforation device; a resettable sealing device operatively assembled with the perforation device for deployment on tubing string; a sliding member operatively associated with the tubing string, for use in actuation of the resettable sealing device; and a debris relief passageway operatively associated with the sliding member, for use in discharge of settled debris about the sliding member.

In one embodiment, the wellbore is a cased wellbore, and the sliding member is a mechanical casing collar locator having outwardly biased locating members for sliding against the casing to verify the downhole location of the tool assembly prior to actuation of the sealing device. In a further embodiment, the debris relief passageway may comprise one or more apertures through the locating members to allow passage of fluid and debris through the locating members, thereby preventing accumulation of settled debris against the locating members.

In another embodiment, the sliding member is an auto-J profile slidable against a pin for actuation of the sealing member. The debris relief passageway may comprise one or more debris ports through the J-profile to permit discharge of debris upon slidable movement of the pin within the J-profile. In a further embodiment, the J-slot is sized at least 1/16 inch greater than the pin, to allow debris accumulation and movement within the J-profile without impeding travel of the pin along the J-profile. The pin may be held to the assembly by a clutch ring, and the clutch ring may comprise debris relief passageways to permit discharge of debris from about the pin while the pin slides within the J-profile.

In another embodiment, the sliding member is an equalization valve actuable to open a flowpath within the sealing device, for unseating the sealing device from the wellbore. In a further embodiment, the equalization valve comprises an equalization plug slidable within an equalization valve housing. The equalization plug, in one embodiment, may be actuated by application of force to the tubing string.

In certain embodiments, the perforation device is a fluid jet perforation device assembled above the sealing device. In a further embodiment, the resettable sealing device comprises a compressible sealing element actuated by the sliding of a pin within an auto J profile. The J profile may comprise debris ports for discharging debris upon slidable movement of the pin within the J-profile.

In one embodiment, the J-slot is sized at least 1/16 inch greater (in width and/or depth) than the pin, to allow debris accumulation and movement within the J-profile without impeding travel of the pin along the J-profile.

The pin, in any of the above-mentioned embodiments, may be held to the assembly by a clutch ring comprising debris relief passageways to permit discharge of debris from about the pin while the pin slides within the J-profile.

In another embodiment, the assembly further comprises a mechanical casing collar locator having outwardly biased locating members for sliding against the casing to verify the downhole location of the tool assembly prior to actuation of the sealing device. One or more apertures through the mandrel and/or locating members may be present to allow passage of fluid and debris through the locating members, thereby preventing accumulation of settled debris against the locating members.

In accordance with another aspect of the invention, there is provided a multi-function valve for use within a downhole assembly deployed on tubing string, the multi-function valve comprising: a valve housing having an internal cavity continuous with a length of tubing string and with a lower assembly mandrel, the valve housing further comprising at least one cross flow port, to permit fluid cross flow through the internal cavity; a forward flow-stop valve operatively associated with the valve housing, for preventing fluid flow from the tubing string into the valve housing; a valve plug slidably disposed within the valve housing for movement between a flow position and a sealed position, the valve plug comprising: an internal fluid flowpath continuous with the forward flow-stop valve and with the cross flow port of the valve housing when the valve plug is in either the sealed or flow position, and, a valve stem for sealing within the lower assembly mandrel when the valve plug is in the sealed position, to prevent fluid communication between the internal cavity of the valve housing and the lower assembly mandrel.

In one embodiment, the valve plug is operationally coupled to the tubing string so as to be actuable upon application of force to the tubing string.

In accordance with another aspect of the invention, there is provided a method for abrasive perforation and treatment of a formation intersected by a cased wellbore, the method comprising the steps of: deploying a tool assembly within the wellbore on tubing string, the tool assembly comprising a fluid jet perforation device and a sealing device; setting the sealing device against the wellbore; jetting abrasive fluid from the perforation device to perforate the wellbore casing; and circulating treatment fluid down the wellbore annulus to treat the perforations and to flow solids through at least a portion of the tool assembly.

In one embodiment, the sealing device comprises a compressible sealing element actuated by application of force to the tubing string. In a further embodiment, the sealing device is actuated by sliding of a pin within an auto-J profile in response to an application of force to the tubing string.

In an embodiment, the abrasive fluid comprises sand. The treatment fluid may comprise flowable solids.

In an embodiment, the method comprises the step of delivering fluid to the tubing string while treatment is delivered down the wellbore annulus.

In various embodiments, the method further comprises the steps of: monitoring the rate and pressure of fluid delivery down the tubing string; monitoring the rate and pressure of fluid delivery down the wellbore annulus; and estimating the fracture extension pressure during treatment.

In an embodiment, the method further comprises the step of reverse circulating fluid from the wellbore annulus to surface through the tubing string.

In another embodiment, the method further comprises the step of equalizing pressure above and below the sealing device by applying a force to the tubing string to actuate an equalization valve.

In another embodiment, the method further comprises the step of equalizing pressure between the tubing string and wellbore annulus without unseating the sealing device from the wellbore casing.

In another embodiment, the method further comprises the step of moving the tool assembly to another wellbore interval and repeating any or all of the above steps.

In another embodiment, the method further comprises the step of opening an equalization passage from beneath the sealing device to the wellbore annulus above the sealing device.

In accordance with another aspect, there is provided a mechanical casing collar locator for use within a downhole tool assembly, the mechanical casing collar locator comprising outwardly biased locating members for sliding against the casing to verify the downhole location of the tool assembly prior to actuation of the sealing device.

In accordance with one embodiment, the collar locator comprises one or more apertures through the locating members to allow passage of fluid and debris through the locating members, thereby preventing accumulation of settled debris against the locating members.

In accordance with another aspect, there is provided an actuation device for use with a resettable downhole tool in the presence of flowable solids, the actuation device comprising a pin slidable within an auto J profile, wherein the auto J profile comprises debris ports for discharging debris upon slidable movement of the pin within the J-profile.

In one embodiment, the J-slot is sized at least 1/16 inch greater than the pin, to allow debris accumulation and movement within the J-profile without impeding travel of the pin along the J-profile. The pin may be held to the assembly by a clutch ring comprising debris relief passageways to permit discharge of debris from about the pin while the pin slides within the J-profile.

Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Embodiments of the present invention will now be described, by way of example only, with reference to the attached drawing figures, wherein:

FIG. 1A is a perspective view of a tool assembly, in one embodiment, for use in accordance with the methods described herein;

FIG. 1B is a schematic cross-sectional view of the equalizing valve and housing shown in FIG. 1A;

FIG. 2A is a perspective view of a tool assembly, in another embodiment, for use in accordance with the methods described herein;

FIG. 2B is a schematic cross-sectional view of the equalizing valve 24 shown in FIG. 2A;

FIG. 3 is a schematic cross-sectional view of a ported sub, in one embodiment, with hydraulically actuated sliding sleeve port for use in accordance with the methods described herein;

FIG. 4A is a perspective, partial cross-section view of a ported sub having an internal mechanically operated sliding sleeve;

FIG. 4B is a perspective, cross-section view of the ported sub of FIG. 4A, with the sliding sleeve shifted to an open port position;

FIG. 5A is a perspective, partial cross-section view of the tool shown in FIG. 1a , disposed within the ported sub shown in FIG. 4A;

FIG. 5B is a partial cross-sectional perspective view of the tool shown in FIG. 1A, disposed within the ported sub as shown in FIG. 4B;

FIG. 6 is a perspective view of a tool assembly deployed within a wellbore in accordance with one embodiment, with the wellbore shown in cross section;

FIG. 7 is a cross sectional view of a jet perforation device in accordance with one embodiment;

FIG. 8 is a cross sectional view of an equalization device in accordance with one embodiment;

FIG. 9A is a cross sectional view of the equalization plug 141 shown in FIG. 8;

FIG. 9B is a cross sectional of the equalization valve housing 145 shown in FIG. 8;

FIG. 10 is a cross sectional view of a portion of a tool assembly in accordance with one embodiment, in which the equalization device of FIG. 8 is shown assembled with a sealing device 130;

FIG. 11A is a perspective and partial cutaway view of the sealing assembly mandrel 135 shown in FIG. 8;

FIG. 11B is a diagram of the J-profile applied to the sealing assembly mandrel shown in FIG. 10;

FIGS. 11C and 11D are top and side views, respectively, of the clutch ring 136 shown in FIG. 10; and,

FIG. 12 is a perspective and partial cutaway view of a mechanical casing collar locator for use within a tool assembly in accordance with one embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Tools and methods for use in selective opening of ports within a tubular are described. Ported tubular may be run in hole as collars, subs, or sleeves between lengths of tubing, and cemented in place. The ported tubulars are spaced at intervals generally corresponding to desired treatment locations. Within each, one or more treatment ports extends through the tubular, forming a fluid delivery conduit from the tubular to the formation (that is, through the casing or tubular). Accordingly, treatment fluids applied within the tubing may exit through the ports to reach the surrounding formation.

The ported tubulars may be closed with a sliding sleeve to prevent fluid access to the ports. Such sleeves may be shifted or opened by various means. For example, a tool assembly may interlock or mate with the tubular to confirm downhole position of the tool assembly, and the generally cylindrical sleeve may then be gripped to mechanically drive the sleeve open. In another embodiment, pressurized fluid may be selectively applied to a specific location to open a port or slide a sleeve as appropriate.

With reference to the embodiments shown in FIGS. 1 and 2, the tool assemblies generally described below include a sealing member to facilitate isolation of a wellbore portion containing one or more ported tubulars. A perforation device is also present within the tool assembly. Should additional perforations be desired, for example if specific ports will not open, or should the ports clog or otherwise fail to take up or produce fluids, a new perforation can be created without removal of the tool assembly from the wellbore. Such new perforations may be placed within the ported tubular or elsewhere along the wellbore.

The Applicants have previously developed a tool and method for use in the perforation and treatment of multiple wellbore intervals. That tool includes a jet perforation device and isolation assembly, with an equalization valve for controlling fluid flow through and about the assembly. Fluid treatment is applied down the wellbore annulus to treat the perforated zone.

The Applicants have also developed a downhole straddle treatment assembly and method for use in fracturing multiple intervals of a wellbore without removing the tool string from the wellbore between intervals. Further, a perforation device may be present within the assembly to allow additional perforations to be created and treated as desired, in a single trip downhole.

In the present description, the terms “above/below” and “upper/lower” are used for ease of understanding, and are generally intended to mean the relative uphole and downhole direction from surface. However, these terms may be imprecise in certain embodiments depending on the configuration of the wellbore. For example, in a horizontal wellbore one device may not be above another, but instead will be closer (uphole, above) or further (downhole, below) from the point of entry into the wellbore. Likewise, the term “surface” is intended to mean the point of entry into the wellbore, that is, the work floor where the assembly is inserted into the wellbore.

Jet perforation, as mentioned herein, refers to the technique of delivering abrasive fluid at high velocity so as to erode the wall of a wellbore at a particular location, creating a perforation. Typically, abrasive fluid is jetted from nozzles arranged about a mandrel such that the high rate of flow will jet the abrasive fluid from the nozzles toward the wellbore casing. Sand jetting refers to the practice of using sand as the abrasive agent, in an appropriate carrier fluid. For example, typical carrier fluids for use in sand jetting compositions may include one or more of: water, hydrocarbon-based fluids, propane, carbon dioxide, nitrogen assisted water, and the like. As the life of a sand jetting assembly is finite, use of ported collars as the primary treatment delivery route minimizes the need for use of the sand jetting device. However, when needed, the sand jetting device may be used as a secondary means to gain access to the formation should treatment through a particular ported collar fail.

The ported tubulars referred to herein are tubular components or assemblies of the type typically used downhole, having one or more fluid ports through a wall to permit fluid delivery from the inside of the tubular to the outside. For example, ported tubular include stationary and sliding sleeves, collars and assemblies for use in connection of adjacent lengths of tubing, or subs and assemblies for placement downhole. In some embodiments, the ports may be covered and selectively opened. The ported tubulars may be assembled with lengths of non-ported tubing such as casing or production liner, for use in casing or lining a wellbore, or otherwise for placement within the wellbore.

Ported Casing Collars

Selective application of treatment fluid to individual ports, or to groups of ports, is possible using one or more of the methods described here. That is, selective, sequential application of fluid treatment to the formation at various locations along the wellbore is facilitated, in one embodiment, by providing a sliding member, such as a sleeve, piston, valve, or other cover that conceals a treatment port within a wellbore tubular, effectively sealing the port to the passage of fluid. For example, the sliding member may be initially biased or held over the treatment port, and may be selectively moved to allow fluid treatment to reach the formation through the opened port. In the embodiments shown in the Figures, the ported tubular and sleeves are shown as collars or subs for attachment of adjacent lengths of wellbore casing. It is, however, contemplated that a similar port opening configuration could be used in other applications, that is with other tubular members, sleeves, liners, and the like, whether cemented in hole, deployed on tubing string, assembled with production liner, or otherwise positioned within a wellbore, pipe, or tubular.

Other mechanisms may be used to temporarily cover the port until treatment is desired. For example, a burst disc, spring-biased valve, dissolvable materials, and the like, may be placed within the assembly for selective removal to permit individual treatment at each casing collar.

In the ported collar 30 shown in FIG. 3, an annular channel 35 extends longitudinally within the collar 30 and intersects the treatment ports 31. A sliding sleeve 32 within the channel 35 is held over the treatment ports 31 by a shear pin 33. The channel 35 is open to the inner wellbore near each end at sleeve ports 34 a, 34 b. The sliding sleeve 32 is generally held or biased to the closed position covering the port 31, but may be slidably actuated within the channel 35 to open the treatment port 31. For example, a seal may be positioned between the sleeve ports to allow application of fluid to sleeve port 34 a (without corresponding application of hydraulic pressure through sleeve port 34 b). As a result, the sleeve 32 will slide within the channel 35 toward opposing sleeve port 34 b, opening the treatment port 31. Treatment may then be applied to formation through the port 31. The port may or may not be locked open, and may remain open after treatment. In some embodiments, the port may be closed after treatment.

With reference to FIGS. 4a and 4b , a ported sub 40 with an outer housing and inner sliding sleeve 41 is shown in port closed and port open positions, respectively. The sub may be used to connect lengths of casing or tubing as the tubing is made up at surface, prior to running in hole and securing in place with cement or external packers as desired. Ports 42 are formed through the sub 40, but not within the sliding sleeve 41. That is, the ports are closed when the sleeve is positioned as shown in FIG. 4A. The closed sleeve position may be secured against the collar ports using shear pins 43 or other fasteners, by interlocking or mating with a profile on the inner surface of the casing collar, or by other suitable means.

While the sleeve 41 is slidably disposed against the inner surface of the sub in the port closed position, held by shear pin 43, one or more seals 44 prevent fluid flow between these surfaces. If locking of the sleeve in the port open position is desired once the sleeve has been shifted, a lockdown, snap ring 45, collet, or other engagement device may be secured about the outer circumference of the sleeve 41. A corresponding trap ring 47 having a profile, groove, or trap to engage the snap ring 46, is appropriately positioned within the sub so as to engage the snap ring once the sleeve has shifted, holding the sleeve open. Accordingly, a downhole force and/or pressure may be applied to the sliding sleeve to drive the sleeve 41 in the downhole direction, shearing the pin 43 and sliding the sleeve 41 so as to open the ports 42 and lock it open. The inner surface of the sleeve is smooth and consistent in diameter, and is also comparable in inner diameter to that of the connected lengths of tubing so as not to provide a profile narrower than the inner diameter of the tubing. That is, the sleeve does not provide any barrier or surface that will impede the passage of a work string or tool down the tubing.

The unprofiled, smooth nature of the inner surface of the sliding sleeve resists engagement of the sleeve by tools or work strings that may pass downhole for various purposes, and will only be engageable by a gripping device that exerts pressure radially outward, when applied directly to the sleeve. That is, the inner surface of the sleeve is substantially identical to the inner surfaces of the lengths of adjacent pipe. The only aberration in this profile exists within the ported sub at the bottom of each unshifted sliding sleeve, or at the top of each shifted sliding sleeve, where a radially enlarged portion of the sub (absent the concentric sliding sleeve) may be detected. In unshifted sleeves, the radially enlarged portion below the unshifted sleeve may be used to locate unshifted sleeves and position a shifting tool. The absence of such a space (inability to locate) may be used to confirm that shifting of the sleeve has occurred.

Despite the absence of an engagement profile to assist in shifting the sleeve, the sleeve may be shifted by engagement with a sealing member, packer, slips, metal or elastomeric seals, chevron seals, or molded seals. Such seals will engage the sliding sleeve by exerting a force radially outward against the sleeve. In some embodiments, such engagement also provides a hydraulic seal. Thus, once engaged, the sleeve may be shifted by application of mechanical force and/or hydraulic pressure.

The appropriate design and placement of ported collars or subs along a casing to provide perforations or ports through the tubular will minimize the need for tripping in and out of hole to add perforations during completion operations. Further, use of the present tool assemblies for shifting sliding sleeves will also provide efficiencies in completion operations by providing a secondary perforation means deployed on the work string. As perforation is generally time-consuming, hazardous, and costly, any reduction in these operations improves efficiency and safety. In addition, when the pre-placed perforations can be selectively opened during a completion operation, this provides more flexibility to the well operator.

The sleeves may further be configured to prevent locking in the open position, so the ports may be closed after treatment is complete, for example by sliding the sleeve into its original position over the ports.

Tool Assembly

The tool assembly described herein includes at least a sealing member and a perforation device. The sealing member allows some degree of isolation during application of treatment fluid. The perforation device allows a new perforation to be created in the event that fluid treatment is unsuccessful, or when treatment of additional wellbore locations not containing a ported tubular is desired. Notably, the present tool assembly allows integration of secondary perforating capacity within a fluid treatment operation, without removal of the treatment assembly from the wellbore, and without running a separate tool string downhole. In some embodiments, the new perforation may be created, and treatment applied, without adjusting the downhole location of the work string.

With reference to FIG. 1A and FIG. 1B, and to Applicants' U.S. patent application Ser. No. 12/708,709 now issued as U.S. Pat. No. 8,490,702, the content of which is incorporated herein by reference, the Applicants have described a sand jetting tool 100 and method for use in the perforation and treatment of multiple wellbore intervals. That tool included a jet perforation device 10 and a compressible sealing member 11, with an equalization valve 12 for controlling fluid flow through and about the assembly. The setting/unsetting of the sealing member using slips 14, and control over the position of the equalization valve, are both effected by application of mechanical force to the tubing string, which drives movement of a pin within an auto J profile about the tool mandrel, with various pin stop positions corresponding to set and unset seal positions. Fluid treatment is applied down the wellbore annulus when the sealing member is set, to treat the uppermost perforated zone(s). New perforations can be jetted in the wellbore by delivery of abrasive fluid down the tubing string, to reach jet nozzles.

With reference to FIG. 2, and to Applicants' U.S. patent application Ser. No. 13/078,584 now issued as U.S. Pat. No. 8,201,631, the content of which is incorporated herein by reference, the Applicants have also described a straddle assembly and method for use in fracturing multiple intervals of a wellbore without removing the work string from the wellbore between intervals. Upper straddle device 20 includes upper and lower cup seals 22, 23 around treatment apertures 21. Accordingly, fluid applied to the tubing string exits the assembly at apertures 21 and causes cup seals 22, 23 to flare and seal against the casing, isolating a particular perforation within a straddle zone, to receive treatment fluid. A bypass below the cup seals may be opened within the tool assembly, allowing fluid to continue down the inside of the tool assembly to be jetted from nozzles 26 along a fluid jet perforation device 25. An additional anchor assembly 24 may also be present to further maintain the position of the tool assembly within the wellbore, and to assist in opening and closing the bypass valve as necessary.

With reference to FIG. 5A, a work string for use in mechanically shifting a sliding sleeve is shown. In the embodiment shown, a casing collar locator 13 engages a corresponding profile below the unshifted sleeve within the ported tubular, the profile defined by the lower inner surface of the collar and the lower annular surface of the sliding sleeve. Once the collar locator 13 is thus engaged, a seal 11 may be set against the sliding sleeve, aided by mechanical slips 14. The set seal, for example a packer assembly having a compressible sealing element, effectively isolates the wellbore above the ported sub of interest. As force and/or hydraulic pressure is applied to the work string and packer from uphole, the sliding sleeve will be drawn downhole, shearing the pins holding the sleeve to the housing and collapsing collar locator 13. The applied force and/or pressure may be a mechanical force applied directly to the work string (and thereby to the engaged sliding sleeve) from surface, for example coiled tubing, jointed pipe, or other tubing string. The applied force and/or pressure may be a hydraulic pressure applied against the seal through the wellbore annulus, and/or through the work string. Any combination of forces/pressures may be applied once the seal 11 is engaged with the sliding sleeve 41, to shift the sleeve from their original position covering the ports 42. For example, the wellbore and work string may be pressurized appropriately with fluid to aid the mechanical application of force to the work string and shift the sleeve. In various embodiments, some or all of the shifting may be accomplished by mechanical force, and in other embodiments by hydraulic pressure. In many embodiments, a suitable combination of mechanical force and hydraulic pressure will be sufficient to shift the sleeve from their position covering the ports.

With reference to FIG. 5B, once the lower inner surface of the collar meets the lower annular surface of the sliding sleeve, the ports 42 are open and treatment may be applied to the formation. Further, with the sliding sleeve meeting the lower inner surface of the collar, there is no longer a locatable profile for engagement by the corresponding tubing deployed dogs/collar locator. Accordingly, the work string may be run through the sleeve without overpull, to verify that the sleeve has been opened.

Notably, after the sleeve has been opened, the seal and work string may remain set within the wellbore to isolate the ports in the newly opened sleeve from any previously opened ports below. Alternatively, the seal may be unset for verifying the state of the opened sleeve, or to relocate the work string as necessary (for example to apply treatment fluid to the ports of one or more collars simultaneously). Depending on the configuration of the work string, treatment fluid may be applied to the ports through one or more apertures in the work string, or via the wellbore annulus about the work string.

It is noted that the work string and components, and the sliding sleeve and casing collar shown and discussed herein, are provided as examples of suitable embodiments for opening variously configured downhole ports. Numerous modifications are contemplated and will be evident to those reading the present disclosure. For example, while downhole shifting of the sliding sleeves shown in FIGS. 3 and 4 is described herein, the sleeve, collar and work string components could be reversed such that the sleeve is shifted uphole to open the ports. Further, various forms of locating the collars and sleeves, and of shifting the sleeves, are possible. Notably, either of the tool assemblies shown in FIG. 1 or FIG. 2 could be used to actuate either of the sliding sleeves depicted in FIG. 3 or 4 and to treat the formation through the opened ports. Various combinations of elements are possible within the scope of the teachings provided herein.

Method

When lining a wellbore for use as discussed herein, casing is made up and run in hole, and a predetermined number of ported collars are incorporated between sections of casing at predetermined spacing. Once the casing string is in position within the wellbore, it is cemented into place. While the cementing operation may cover the outer ports of the ported collars, the cement plugs between the ported collar and the formation are easily displaced upon delivery of treatment fluid through each port as will be described below. If the well remains uncemented and the ported collars are additionally isolated using external seals, there is no need to displace cement.

Once the wellbore is ready for completion operations, a tool assembly with at least one sealing or anchor member and a jet perforation device is run in hole on coiled tubing. Depending on the configuration of the well, the tool assembly, and the method of operation of the ported collars, a particular ported sub of interest is selected and the tool assembly is positioned appropriately. Typically, the ported subs will be actuated and the well treated starting at the bottom/lowermost/deepest collar and working uphole. Appropriate depth monitoring systems are known in the art, and can be used with the tool assembly in vertical, horizontal, or other wellbores as desired to ensure accurate positioning of the tool assembly.

Specifically, when positioning the tool assembly for operating the sliding sleeve of the ported sub shown in FIG. 3, a sealing member of the tool assembly is positioned between the sleeve ports of a single ported sub to isolate the paired sleeve ports on either side of the sealing member. Thus, when fluid is applied to the wellbore, fluid will enter the annular channel 35 at the ported collar of interest through only one of the sleeve ports, as the other sleeve port will be on the opposing side of the sealing member and will not take up fluid to balance the sleeve within the channel. In the ported collar shown in FIG. 3, fluid would be applied only to the upper sleeve port 34 a. Accordingly, the flow of fluid into the annular channel from only one end will create hydraulic pressure within the upper portion of the annular channel, ultimately shearing the pin holding the sliding sleeve in place. The sliding sleeve will be displaced within the channel, uncovering the treatment port and allowing the passage of pressurized treatment fluid through the port, through the cement, and into the formation.

For greater clarity, the ported sub shown in FIG. 3 is opened as a result of a sealing member being positioned between its sleeve ports, which allows only one sleeve port to receive fluid, pressurizing the channel to shear the pin holding the sliding sleeve over the treatment port (or in other embodiments, forcing open the biased treatment port closure). The treatment ports within the remainder of the ported collars along the wellbore will not be opened, as fluid will generally enter both sleeve ports equally, maintaining the balanced position of the sliding sleeve over the ports in those collars.

Once treatment has been fully applied to the opened port, for example either through the tubing or down the annulus, application of treatment fluid to the port is terminated, and the hydraulic pressure across the annular channel is dissipated. If the sliding sleeve is biased to close the treatment port, the treatment port may close when application of treatment fluid ceases. However, closure of the treatment port is not required, particularly when treatment is applied to wellbore intervals moving from the bottom of the well towards surface. That is, once treatment of the first wellbore segment is terminated, the tool assembly is moved uphole to position a sealing member between the sleeve ports of the next ported sub to be treated. Accordingly, the previously treated collar is inherently isolated from receiving further treatment fluid, and the ports may continue to be treated independently.

When a tool string having a straddle sealing assembly is available, the tool assembly may be used in at least two distinct ways to shift a sleeve. In the first instance, the straddle tool may be used in the method described above, setting the lower sealing member between the sleeve ports of a ported sub of interest and applying treatment fluid down the tubing string.

Alternatively, the method may be altered when using a straddle sealing assembly to allow the ported collars to be treated in any order. Specifically, one of the sealing members (in the assembly shown in FIG. 2, the lower sealing member) is set between the sleeve ports of a ported collar of interest. Treatment fluid may be applied down the tubing string to the isolated interval, which will enter only the upper sleeve port, creating a hydraulic pressure differential across the sliding sleeve and forcing the treatment port open.

Should the ported collar fail to open, or treatment through the ported collar be otherwise unsuccessful, the jet perforation device may be used to create a new perforation in the casing. Once the new perforation has been jetted, treatment can continue.

The method therefore allows treatment of pre-existing perforations (such as ported casing collars) within a wellbore, and creation of new perforations for treatment, as needed, with a single tool assembly and in a single trip downhole.

Example 1

Tool Assembly with Single Sealing Member

With reference to the tool assembly shown in FIG. 1, a fluid jetting device is provided for creating perforations through a liner, and a sealing device is provided for use in the isolation and treatment of a perforated interval. Typically, when carrying out a standard completion operation, the tool string is assembled and deployed downhole on tubing (for example coiled tubing or jointed pipe) to the lowermost interval of interest. The sealing device 11 is set against the casing of the wellbore, abrasive fluid is jetted against the casing to create perforations, and then a fluid treatment (for example a fracturing fluid) is injected down the wellbore annulus from surface under pressure, which enters the formation via the perforations. Once the treatment is complete, the hydraulic pressure in the annulus is slowly dissipated, and the sealing device 11 is released. The tool may then be moved up-hole to the next interval of interest.

Notably, both forward and reverse circulation flowpaths between the wellbore annulus and the inner mandrel of the tool string are present to allow debris to be carried in the forward or reverse direction through the tool string. Further, the tubing string may be used as a dead leg during treatment down the annulus, to allow pressure monitoring for early detection of adverse events during treatment, to allow prompt action in relieving debris accumulation, or maximizing the stimulation treatment.

When using the tool string in accordance with the present method, perforation is a secondary function. That is, abrasive jet perforation would generally be used only when a ported collar fails to open, when fluid treatment otherwise fails in a particular zone, or when the operation otherwise requires creation of a new perforation within that interval. The presence of the ported subs between tubulars will minimize the use of the abrasive jetting device, and as a result allow more stages of treatment to be completed in a single wellbore in less time. Each ported collar through which treatment fluid is successfully delivered reduces the number of abrasive perforation operations, thereby reducing time and costs by reducing fluid and sand delivery requirements (and later disposal requirements when the well is put on production), increases the number of zones that can be treated in a single trip, and also extends the life of the jetting device.

When abrasive fluid perforation is required, and has been successfully completed, the jetted fluid may be circulated from the wellbore to surface by flushing the tubing string or casing string with an alternate fluid prior to treatment application to the perforations. During treatment of the perforations by application of fluid to the wellbore annulus, a second volume of fluid (which may be a second volume of the treatment fluid, a clear fluid, or any other suitable fluid) may also be pumped down the tubing string to the jet nozzles to avoid collapse of the tubing string and prevent clogging of the jet nozzles.

As shown in the embodiment illustrated in FIG. 1, the sealing device 11 is typically positioned downhole of the fluid jetting assembly 10. This configuration allows the seal to be set against the tubular, used as a shifting tool to shift the sleeve, provide a hydraulic seal to direct fluid treatment to the perforations, and, if desired, to create additional perforations in the tubular. Alternatively, the seal may be located anywhere along the tool assembly, and the tool string may re-positioned as necessary.

Suitable sealing devices will permit isolation of the most recently perforated or port-opened interval from previously treated portions of the wellbore below. For example, inflatable packers, compressible packers, bridge plugs, friction cups, straddle packers, and others known in the art may be useful for this purpose. The sealing device is able to set against any tubular surface, and does not require a particular profile at the sleeve in order to provide suitable setting or for use in shifting of an inner sliding sleeve, as such a profile may otherwise interfere with the use of other tools downhole. The sealing device may be used with any ported sub to hydraulically isolate a portion of the wellbore, or the sealing device may be used to set a hydraulic seal directly against an inner sliding sleeve to provide physical shifting of the sleeve, for example to open ports. The sealing device also allows pressure testing of the sealing element prior to treatment, and enables reliable monitoring of the treatment application pressure and bottomhole pressure during treatment. The significance of this monitoring will be explained below.

Perforation and treatment of precise locations along a vertical, horizontal, or deviated wellbore may be accomplished by incorporation of a depth locating device within the assembly. This will ensure that when abrasive fluid perforation is required, the perforations are located at the desired depth. Notably, a mechanical casing collar locator permits precise depth control of the sealing and anchoring device in advance of perforation, and maintains the position of the assembly during perforation and treatment. The collar locator may also be used to locate a work string at unshifted sleeves of the type shown in FIG. 5A.

When this tool assembly is used for perforation, the sealing device is set against the casing prior to perforation, as this may assist in maintaining the position and orientation of the tool string during perforation and treatment of the wellbore. Alternatively, the sealing assembly may be actuated following perforation. In either case, the sealing assembly is set against the casing beneath the perforated interval of interest, to hydraulically isolate the lower wellbore (which may have been previously perforated and treated) from the interval to be treated. That is, the seal defines the lower limit of the wellbore interval to be treated. Typically, this lower limit will be downhole of the most recently formed perforations, but up-hole of any previously treated jetted perforations or otherwise treated ports. Such configuration will enable treatment fluid to be delivered to the most recently formed perforations by application of said treatment fluid to the wellbore annulus from surface. Notably, when jetting new perforations in a wellbore having ported subs, in which the ports are covered, unopened ported collars will remain closed during treatment of the jetted perforation, and as a result such newly jetted perforations may be treated in isolation.

As shown, the sealing assembly 11 is mechanically actuated, including a compressible sealing element for providing a hydraulic seal between the tool string and casing when actuated, and slips 14 for engaging the casing to set the compressible sealing element. In the embodiment shown, the mechanism for setting the sealing assembly involves a stationary pin sliding within a J profile formed about the sealing assembly mandrel. The pin is held in place against the bottom sub mandrel by a two-piece clutch ring, and the bottom sub mandrel slides over the sealing assembly mandrel, which bears the J profile. The clutch ring has debris relief openings for allowing passage of fluid and solids during sliding of the pin within the J profile. Debris relief apertures are present at various locations within the J-profile to permit discharge of settled solids as the pin slides within the J profile. The J slots are also deeper than would generally be required based on the pin length alone, which further provides accommodation for debris accumulation and relief without inhibiting actuation of the sealing device. Various J profiles suitable for actuating mechanical set packers and other downhole tools are known within the art.

In order to equalize pressure across the sealing device and permit unsetting of the compressible sealing element under various circumstances, an equalization valve 12 is present within the tool assembly. While prior devices may include a valve for equalizing pressure across the packer, such equalization is typically enabled in one direction only, for example from the wellbore segment below the sealing device to the wellbore annulus above the sealing device. The presently described equalization valve permits constant fluid communication between the tubing string and wellbore annulus, and, when the valve is in fully open position, also with the portion of the wellbore beneath the sealing device. Moreover, fluid and solids may pass in forward or reverse direction between these three compartments. Accordingly, appropriate manipulation of these circulation pathways allows flushing of the assembly, preventing settling of solids against or within the assembly. Should a blockage occur, further manipulation of the assembly and appropriate fluid selection will allow forward or reverse circulation to the perforations to clear the blockage.

As shown in FIG. 1B, the equalization valve is operated by sliding movement of an equalization plug 15 within a valve housing 16. Such slidable movement is actuated from surface by pulling or pushing on the coiled tubing, which is anchored to the assembly by a main pull tube. The main pull tube is generally cylindrical and contains a ball and seat valve to prevent backflow of fluids through from the equalization valve to the tubing string during application of fluid through the jet nozzles (located upstream of the pull tube). The equalization plug 15 is anchored over the pull tube, forming an upper shoulder that limits the extent of travel of the equalization plug 15 within the valve housing 16. Specifically, an upper lock nut is attached to the valve housing and seals against the outer surface of the pull tube, defining a stop for abutment against the upper shoulder of the equalization plug.

The lower end of the valve housing 16 is anchored over assembly mandrel, defining a lowermost limit to which the equalization plug 15 may travel within the valve housing 16. It should be noted that the equalization plug bears a hollow cylindrical core that extends from the upper end of the equalization plug 15 to the inner ports 17. That is, the equalization plug 15 is closed at its lower end beneath the inner ports, forming a profiled solid cylindrical plug 18 overlaid with a bonded seal. The solid plug end and bonded seal are sized to engage the inner diameter of the lower tool mandrel, preventing fluid communication between wellbore annulus/tubing string and the lower wellbore when the equalization plug has reached the lower limit of travel and the sealing device (downhole of the equalization valve) is set against the casing.

The engagement of the bonded seal within the mandrel is sufficient to prevent fluid passage, but may be removed to open the mandrel by applying sufficient pull force to the coiled tubing. This pull force is less than the pull force required to unset the sealing device, as will be discussed below. Accordingly, the equalization valve may be opened by application of pulling force to the tubing string while the sealing device remains set against the wellbore casing. It is advantageous that the pull tube actuates both the equalization plug and the J mechanism, at varying forces to allow selective actuation. However, other mechanisms for providing this functionality may now be apparent to those skilled in this art field and are within the scope of the present teaching.

With respect to debris relief, when the sealing device is set against the wellbore casing with the equalization plug 15 in the sealed, or lowermost, position, the inner ports 17 and outer ports 19 are aligned. This alignment provides two potential circulation flowpaths from surface to the perforations, which may be manipulated from surface as will be described. That is, fluid may be circulated to the perforations by flushing the wellbore annulus alone. During this flushing, a sufficient fluid volume is also delivered through the tubing string to maintain the ball valve within the pull tube in seated position, to prevent collapse of the tubing, and to prevent clogging of the jet nozzles.

Should reverse circulation be required, fluid delivery down the tubing string is terminated, while delivery of fluid to the wellbore annulus continues. As the jet nozzles are of insufficient diameter to receive significant amounts of fluid from the annulus, fluid will instead circulate through the aligned equalization ports, unseating the ball within the pull tube, and thereby providing a return fluid flowpath to surface through the tubing string. Accordingly, the wellbore annulus may be flushed by forward or reverse circulation when the sealing device is actuated and the equalization plug is in the lowermost position.

When the sealing device is to be released (after flushing of the annulus, if necessary to remove solids or other debris), a pulling force is applied to the tubing string to unseat the cylindrical plug 15 and bonded seal from within the lower mandrel. This will allow equalization of pressure beneath and above the seal, allowing it to be unset and moved up-hole to the next interval.

Components may be duplicated within the assembly, and spaced apart as desired, for example by connecting one or more blast joints within the assembly. This spacing may be used to protect the tool assembly components from abrasive damage downhole, such as when solids are expelled from the perforations following pressurized treatment. For example, the perforating device may be spaced above the equalizing valve and sealing device using blast joints such that the blast joints receive the initial abrasive fluid expelled from the perforations as treatment is terminated and the tool is pulled uphole.

The equalization valve therefore serves as a multi-function valve in the sealed, or lowermost position, forward or reverse circulation may be effected by manipulation of fluids applied to the tubing string and/or wellbore annulus from surface. Further, the equalization plug may be unset from the sealed position to allow fluid flow to/from the lower tool mandrel, continuous with the tubing string upon which the assembly is deployed. When the equalization plug is associated with a sealing device, this action will allow pressure equalization across the sealing device.

Notably, using the presently described valve and suitable variants, fluid may be circulated through the valve housing when the equalization valve is in any position, providing constant flow through the valve housing to prevent clogging with debris. Accordingly, the equalization valve may be particularly useful in sand-laden environments.

During the application of treatment to the perforations via the wellbore annulus, the formation may stop taking up fluid, and the sand suspended within the fracturing fluid may settle within the fracture, at the perforation, on the packer, and/or against the tool assembly. As further circulation of proppant-laden fluid down the annulus will cause further undesirable solids accumulation, early notification of such an event is important for successful clearing of the annulus and, ultimately, removal of the tool string from the wellbore. A method for monitoring and early notification of such events is possible using this tool assembly.

During treatment down the wellbore annulus using the tool string shown in FIG. 1, fluid will typically be delivered down the tubing string at a constant (minimal) rate to maintain pressure within the tubing string and keep the jet nozzles clear. The pressure required to maintain this fluid delivery may be monitored from surface. The pressure during delivery of treatment fluid to the perforations via the wellbore annulus is likewise monitored. Accordingly, the tubing string may be used as a “dead leg” to accurately calculate (estimate/determine) the fracture extension pressure by eliminating the pressure that is otherwise lost to friction during treatment applied to the wellbore. By understanding the fracture extension pressure trend (also referred to as stimulation extension pressure), early detection of solids accumulation at the perforations is possible. That is, the operator will quickly recognize a failure of the formation to take up further treatment fluid by comparing the pressure trend during delivery of treatment fluid down the wellbore annulus with the pressure trend during delivery of fluid down the tubing string. Early recognition of an inconsistency will allow early intervention to prevent debris accumulation at the perforations and about the tool.

During treatment, a desired volume of fluid is delivered to the formation through the most recently perforated interval, while the remainder of the wellbore below the interval (which may have been previously perforated and treated) is hydraulically isolated from the treatment interval. Should the treatment be successfully delivered down the annulus, the sealing device may be unset by pulling the equalization plug from the lower mandrel. This will equalize pressure between the wellbore annulus and the wellbore beneath the seal. Further pulling force on the tubing string will unset the packer by sliding of the pin to the unset position in the J profile. The assembly may then be moved uphole to perforate and treat another interval.

However, should treatment monitoring suggest that fluid is not being successfully delivered, indicating that solids may be settling within the annulus, various steps may be taken to clear the settled solids from the annulus. For example, pumping rate, viscosity, or composition of the annulus treatment fluid may be altered to circulate solids to surface.

Should the above clearing methods be unsuccessful in correcting the situation (for example if the interval of interest is located a great distance downhole that prevents sufficient circulation rates/pressures at the perforations to clear solids), the operator may initiate a reverse circulation cycle as described above. That is, flow downhole through the tubing string may be terminated to allow annulus fluid to enter the tool string through the equalization ports, unseating the ball valve and allowing upward flow through the tubing string to surface. During such reverse circulation, the equalizer valve remains closed to the annulus beneath the sealing assembly.

A method for deploying and using the above-described tool assembly, and similar functioning tool assemblies, would include the following steps, which may be performed in any logical order based on the particular configuration of tool assembly used: lining a wellbore, wherein the liner comprises one or more ported tubular segments, each ported tubular segment having one or more lateral treatment ports for communication of fluid from inside the liner to outside; running a tool string downhole to a predetermined depth corresponding to one of the ported tubular segments, the tool string including a hydra-jet perforating assembly and a sealing or anchor assembly; setting the isolation assembly against the wellbore casing; pumping a treatment fluid down the wellbore annulus from surface through the ported tubular; and monitoring fracture extension pressure during treatment.

In addition, any or all of the following additional steps may be performed: Engaging a sliding sleeve with the sealing or anchor assembly and applying a force to the sleeve to slide the sleeve; Opening the treatment ports; reverse circulating annulus fluid to surface through the tubing string; equalizing pressure above and below the sealing device or isolation assembly; equalizing pressure between the tubing string and wellbore annulus without unseating same from the casing; unseating the sealing assembly from the casing; repeating any or all of the above steps within the same wellbore interval; creating a new perforation in the casing by jetting abrasive fluid from the hydra-jet perforating assembly; and, moving the tool string to another predetermined interval within the same wellbore and repeating any or all of the above steps.

Should a blockage occur downhole, for example above a sealing device within the assembly, delivery of fluid through the tubing string at rates and pressures sufficient to clear the blockage may not be possible, and likewise, delivery of clear fluid to the wellbore annulus may not dislodge the debris. Accordingly, in such situations, reverse circulation may be effected while the inner and outer ports remain aligned, simply by manipulating the type and rate of fluid delivered to the tubing string and wellbore annulus from surface. Where the hydraulic pressure within the wellbore annulus exceeds the hydraulic pressure down the tubing string (for example when fluid delivery to the tubing string ceases), fluid within the equalization valve will force the ball to unseat, providing reverse circulation to surface through the tubing string, carrying flowable solids.

Further, the plug may be removed from the lower mandrel by application of force to the pull tube (by pulling on the tubing string from surface). In this unseated position, a further flowpath is opened from the lower tool mandrel to the inner valve housing (and thereby to the tubing string and wellbore annulus). Where a sealing device is present beneath the equalization device, pressure across the sealing device will be equalized allowing unsetting of the sealing device.

It should be noted that the fluid flowpath from outer ports 19 to the tubing string is available in any position of the equalization plug. That is, this flowpath is only blocked when the ball is set within the seat based on fluid down tubing string. When the equalization plug is in its lowermost position, the inner and outer ports are aligned to permit flow into and out of the equalization valve, but fluid cannot pass down through the lower assembly mandrel. When the equalization plug is in the unsealed position, the inner and outer ports are not aligned, but fluid may still pass through each set of ports, into and out of the equalization valve. Fluid may also pass to and from the lower assembly mandrel. In either position, when the pressure beneath the ball valve is sufficient to unseat the ball, fluid may also flow upward through the tubing string.

The sealing device may be set against any tubular, including a sliding sleeve as shown in FIG. 4. Once set, application of force (mechanical force or hydraulic pressure) to the sealing device will drive the sliding sleeve downward, opening the ports.

Example 2

Tool Assembly with Straddle Seals

With reference to the tool assembly shown in FIG. 2, a tool string is deployed on tubing string such as jointed pipe, concentric tubing, or coiled tubing. The tool string will typically include: a treatment assembly with upper and lower isolation elements, a treatment aperture between the isolation elements, and a jet perforation device for jetting abrasive fluid against the casing. A bypass valve and anchoring assembly may be present to engage the casing during treatment.

Various sealing devices for use within the tool assembly to isolate the zone of interest are available, including friction cups, inflatable packers, and compressible sealing elements. In the particular embodiments illustrated and discussed herein, friction cups are shown straddling the fracturing ports of the tool. Alternate selections and arrangement of various components of the tool string may be made in accordance with the degree of variation and experimentation typical in this art field.

As shown, the anchor assembly 27 includes an anchor device, an actuator assembly, and a bypass/equalization valve. Suitable anchoring devices may include inflatable packers, compressible packers, drag blocks, and other devices known in the art. The anchor device depicted in FIG. 2 is a set of mechanical slips driven outwardly by downward movement of the cone. The bypass assembly is controlled from surface by applying a mechanical force to the coiled tubing, which drives a pin within an auto J profile about the tool mandrel.

The anchoring device is provided for stability in setting the tool, and to prevent sliding of the tool assembly within the wellbore during treatment. Further, the anchoring device allows controlled actuation of the bypass valve/plug within the housing by application of mechanical force to the tubing string from surface. Simple mechanical actuation of the anchor is generally preferred to provide adequate control over setting of the anchor, and to minimize failure or debris-related jamming during setting and releasing the anchor. Mechanical actuation of the anchor assembly is loosely coupled to actuation of the bypass valve, allowing coordination between these two slidable mechanisms. The presence of a mechanical casing collar locator, or other device providing some degree of friction against the casing, is helpful in providing resistance against which the anchor and bypass/equalization valve may be mechanically actuated.

That is, when placed downhole at an appropriate location, the fingers of the mechanical casing collar locator provide sufficient drag resistance for manipulation of the auto J mechanism by application of force to the tubing string. When the pin is driven towards its downward-most pin stop in the J profile, the cone is driven against the slips, forcing them outward against the casing, acting as an anchor within the wellbore. When used in accordance with the present method, the tool is positioned with one or both sets of friction cups between the sleeve ports 34 of the annular channel 35 in the ported casing collar 30. Treatment fluid is applied to one of the sleeve ports (in the collar shown in FIG. 3, to the upper port 34 a), driving the sliding sleeve 33 downward toward the lower sleeve port 34 b. Once the treatment port 31 has been uncovered, treatment fluid will enter the port. Pressurized delivery of further amounts of fluid will erode any cement behind the port and reach the formation.

With reference to FIG. 2B, the bypass valve includes a bypass plug 24 a slidable within an equalization valve housing 24 b. Such slidable movement is actuated from surface by pulling or pushing on the tubing, which is anchored to the assembly by a main pull tube. The main pull tube is generally cylindrical and provides an open central passageway for fluid communication through the housing from the tubing. The bypass plug 24 a is anchored over the pull tube, forming an upper shoulder that limits the extent of travel of the bypass plug 24 a within the valve housing 24 b. Specifically, an upper lock nut is attached to the valve housing 24 b and seals against the outer surface of the pull tube, defining a stop for abutment against the upper shoulder of the bypass plug 24 a.

The lower end of the valve housing 24 b is anchored over a mandrel, defining a lowermost limit to which the bypass plug 24 a may travel within the valve housing 24 b. The bypass plug 24 a is closed at its lower end, and is overlaid with a bonded seal. This solid plug end and bonded seal are sized to engage the inner diameter of the lower tool assembly mandrel, preventing fluid communication between wellbore annulus/tubing string and the lower wellbore when the bypass plug 24 a has reached the lower limit of travel.

Closing of the bypass prevents fluid passage from the tubing string to below, but the bypass may be opened by applying sufficient pull force to the coiled tubing. This pull force is less than the pull force required to unset the anchor due to the slidability of the bypass plug 24 a within the housing 24 b. Accordingly, the equalization valve may be opened by application of pulling force to the tubing string while the anchor device remains set against the wellbore casing. This allows equalization of pressure from the isolated zone and unsetting of the cup seals without slippage and damage to the cup seals while pressure is being equalized.

Notably, the bypass valve 24 provides a central fluid passageway from the tubing to the lower wellbore. Bypass plug 24 a is slidable within the assembly upon application of force to the tubing string, to open and close the passageway. Notably, while the states of the bypass and anchor are both dependent on application of force to the tubing string from surface, the bypass plug is actuated initially without any movement of the pin within the J slot.

When this tool string is assembled and deployed downhole on tubing for the purpose of shifting the sliding sleeve shown in FIG. 3, it may be positioned with the lower cup between the sleeve ports of a particular ported collar of interest. That is, the lower seals are positioned below the treatment port, but above the lower sleeve port. The bypass valve 24 is closed and the anchor set against the casing, and fluid is pumped down the tubing under pressure, exiting the tubing string at treatment apertures 21, as the closed bypass valve prevents fluid from passing down the tool string to the jet perforation device 25. Fluid delivery through the apertures 11 results in flaring of the friction cups 22, 23, with the flared cups sealing against the casing. Once the cups have sealed against the wellbore, the hydraulic pressure will rise within the isolated interval, and fluid will enter the upper sleeve port, ultimately displacing the sliding sleeve and opening the treatment port. Once opened, continued delivery of fluid will result in erosion of any cement behind the treatment port, and delivery of treatment fluid to the formation.

When treatment is terminated, the bypass valve 24 is pulled open to release pressure from the isolated zone, allowing fluid and debris to flow downhole through the bottom portion of the tool string. Once the pressure within the fractured zone is relieved, the cup seals relax to their running position. When treatment is complete, the cone 29 is removed from engagement with the inwardly-biased slips by manipulation of the pin within the J profile to the release position, allowing retraction of the anchor/slips 28 from the casing. The anchor is thereby unset and the tool string can be moved to the next interval of interest or retrieved from the wellbore.

If perforation of the wellbore is desired, the bypass valve 24 is open and the friction cups are set across the wellbore above the zone to be perforated. Pumping abrasive fluid down the tubing string will deliver fluid preferentially through the treatment ports 11 until the friction cups seal against the wellbore. As this interval is unperforated, once the interval is pressurized, fluid will be directed down the assembly to exit jet nozzles 26. Continued delivery of fluid will result in jetting of abrasive fluid against the casing to perforate the wellbore adjacent the jet nozzles. When fluid pressure is applied the cup seals will engage the casing, and the tool string will remain fixed, stabilizing the jet sub while abrasive fluid is jetted through nozzles 26.

In order to allow fluid delivered to the tubing string to reach jet nozzles 26, the bypass valve must be in the open position. It has been noted during use that when fluid is delivered to the bypass valve at high rates, the pressure within the valve typically tends to drive the valve open. That is, a physical force should be applied to hold the valve closed, for example by setting the anchor. Accordingly, when jet perforation is desired, the valve is opened by pulling the tubing string uphole to the perforation location. When fluid delivery is initiated with the bypass valve open, the hydraulic pressure applied to the tubing string (and through treatment apertures) will cause the cup seals to seal against the casing. If no perforation is present within that interval, the hydraulic pressure within the interval will be maintained between the cups, and further pressurized fluid in the tubing will be forced/jetted through the nozzles 26. Fluid jetted from the nozzles will perforate or erode the casing and, upon continued fluid application, may pass down the wellbore to open perforations in other permeable zones. Typically, the fluid jetted from nozzles 26 will be abrasive fluid, as generally used in sand jet perforating techniques known in the prior art.

Once jetting is accomplished, fluid delivery is typically terminated and the pressure within the tubing string and straddled interval is dissipated. The tool may then be moved to initiate a further perforation, or a treatment operation.

Example 3 Method for Shifting Sliding Sleeve Using Tool Deployed On Coiled Tubing

With reference to the tool assembly shown in FIG. 1 and the sliding sleeve shown in FIG. 4A and FIG. 4B, a method is provided for mechanically shifting a sliding sleeve using a tool deployed downhole on coiled tubing, by application of downhole force to the tool assembly.

The wellbore is cased, with ported subs used to join adjacent lengths of tubing at locations corresponding to where treatment may later be desired. The casing is assembled and cemented in hole with the ports in the closed position, as secured by shear pin 43.

A completion tool having the general configuration as shown in FIG. 1 is attached to coiled tubing and is lowered downhole to a location below the lowermost ported casing collar. The collar locator 13 is of a profile corresponding with the space in the lower end of the collar. That is, the radially enlarged annular space defined between the lowermost edge of the sliding sleeve and the lowermost inner surface of the collar when the sleeve is in the port closed position.

As the tool is slowly pulled upward within the wellbore, the collar locator 13 will become engaged within the above-mentioned radially enlarged annular space, identifying to the operator the position of the tool assembly at the lowermost ported collar to be opened and treated. The packer 11 is set by application of mechanical force to the tubing string, with the aid of mechanical slips 14 to set the packer against the inner surface of the sleeve. Application of this mechanical force will also close the equalization valve 12 such that the wellbore above the packer is hydraulically sealed from the wellbore below. As further mechanical pressure is applied to the coiled tubing, additional downward force may be applied by delivering treatment fluid down the wellbore annulus (and to down the coiled tubing to the extent that will avoid collapse of the tubing). As pressure against the packer, and sliding sleeve 41, builds, the shear pin 43 will shear. The sleeve simultaneously shift down the casing collar to open (or unblock) the ports 42 in the casing collar, allowing treatment fluid to enter the ports and reach the formation. When the sleeve moves down, the collar locator dogs are pushed out of the locating profile. After the zone is treated, the collar locator can move freely through the sleeve since the mandrel is now covering the indicating profile. Free uphole movement of the collar locator past the sleeve confirms that the sleeve is shifted.

During treatment, the operator is monitoring wellbore conditions as in Examples 1 and 2 above. Should it be determined that fluid is not being delivered to the formation through the ports, attempts may be made to use alternate circulation flowpaths to clear a blockage. Should these further attempts to treat the wellbore continue to be unsuccessful, fluid can be delivered at high volumes through the tubing to jet fluid from the perforation nozzles 10 in the tool assembly, while the equalization valve 12 remains closed, to jet new perforations through the casing. The operator may wish to unset the packer and adjust the position of the assembly to prior to jetting such new perforations. Upon re-perforation, treatment of the formation may be continued.

After treatment of the lowermost ported collar is complete, the packer 11 is unset from the wellbore, and the work string is pulled upward until the collar locator engages within another ported collar. The process is repeated, working upwards to surface. This progression, in an upward direction, enables each opened ported collar to be treated in isolation from the remaining wellbore intervals, as only a single opened port will be present above the set packer for each treatment application.

The tool may also be configured to open the ports in a downhole direction, and treatment of the formation could be accomplished in any order with or without isolation of each ported collar from the remaining opened collars during treatment.

With reference to FIG. 6, a fluid jetting device 110 is provided for creating perforations 120 in the casing 181, and a sealing device 130 is provided for use in the isolation and treatment of the perforated interval. The tool string 105 is assembled and deployed downhole on tubing (for example coiled tubing or jointed pipe) to the lowermost interval of interest. The fluid jetting device 110 is then used to perforate the casing 181, providing access to the hydrocarbon-bearing formation 190 surrounding the cased wellbore.

While the sealing device 130 is set against the casing 181 of the wellbore, a fluid treatment (for example a fracturing fluid) is injected down the wellbore annulus 182 from surface under pressure, which enters the formation 190 via the perforations 120, to fracture the formation 190. Once the treatment is complete, the hydraulic pressure in the annulus 182 is slowly dissipated, and the sealing device 130 is released. The tool may then be moved up-hole to the next interval of interest.

As the environment in which the present tool string is used may be sand-laden (due to the formation characteristics, abrasive fluids used in jetting, and/or proppant-laden treatment fluids), there is a significant risk that debris may accumulate within the apertures, slots, chambers, and moving parts of the tool during deployment. For example, jet perforation using abrasive fluid may cause solids to accumulate over the sealing device, if the sealing device is set prior to perforation. Further, when applying a proppant-laden fracturing fluid, proppant and/or formation debris may accumulate over the sealing device, and enter the tool assembly, settling in the moving external and internal workings of the tool. Accordingly, debris relief may be incorporated into the tool, as will be described in detail below.

Briefly, both forward and reverse circulation flowpaths between the wellbore annulus and the inner mandrel of the tool string are provided to allow debris to be carried in the forward or reverse direction through the tool string. Further, debris relief features are incorporated into the moving/sliding parts of the tool string to prevent accumulation of sand, proppant, and other debris that might otherwise prevent actuation or retrieval of the tool. Further, the tubing string may be used as a dead leg during treatment down the annulus, to allow pressure monitoring for early detection of adverse events during treatment, to allow prompt action in relieving debris accumulation.

Fluid Jetting Device

In the embodiment shown in the drawings, the perforation device 110 is an abrasive fluid jet assembly, deployed on tubing string (for example coiled tubing or jointed pipe). Such fluid delivery assemblies with jet nozzles are generally known, and have been used previously in well cleaning operations, application of fracturing treatment, and in placing casing perforations. For perforation operations, pressurized abrasive fluid is applied through the tubing, and is forced through jet nozzles 111 to perforate the wellbore.

In a typical jet perforation assembly 110, nozzles 111 are typically inserts fixed within the perforation mandrel, the nozzles having engineered apertures that allowing pressurized fluid to escape at high velocities. As shown in FIG. 7, jet nozzles 111 are arranged about the perforation mandrel as desired. Typically, about four nozzles is suitable, however the number of nozzles may range from one through about ten or more, depending on the length of the span of the interval to be perforated. A specific volume of abrasive fluid is delivered to the tubing string at a rate suitable for jet perforation of the casing, after which the casing may be tested or treatment initiated to confirm that suitable perforation was effected.

Once perforation is successful, the abrasive jetted fluid may be circulated from the wellbore to surface by flushing the tubing string with an alternate fluid prior to treatment application to the perforations (if desired). During treatment of the perforations by application of fluid to the wellbore annulus 182, a second volume of fluid (which may be a second volume of the treatment fluid, a clear fluid, or any other suitable fluid) may also be pumped down the tubing string to the jet nozzles to avoid collapse of the tubing string and prevent clogging of the jet nozzles.

Alternatively, treatment down the wellbore annulus may be possible without simultaneous delivery of fluid down the tubing string. For example, if the jet nozzles can be closed, the tubing string could be pressurized with fluid to avoid collapse during treatment down the annulus. Other methods for treatment of the perforations using the presently described tool string (with or without modification) are possible, using the knowledge and experience typical of operators in this field of art.

Sealing Device

As shown in the embodiment illustrated in FIG. 6, the sealing device 130 is typically positioned downhole of the fluid jetting assembly 110. This configuration allows the seal to be set against the casing in advance of perforation, if desired, and to remain set until treatment of the perforated interval is complete. Alternatively, the seal may be located anywhere along the tool assembly, and the tool string may repositioned after perforation is complete prior to setting the sealing device below the perforations for treatment.

Suitable sealing devices will permit isolation of the most recently perforated interval from previously treated portions of the wellbore below. For example, inflatable packers, compressible packers, bridge plugs, friction cups, straddle packers, and others known in the art may be useful for this purpose. It is preferable that the sealing device forms a hydraulic seal against the casing to allow pressure testing of the sealing element prior to treatment, and to enable reliable monitoring of the treatment application pressure and bottomhole pressure during treatment. The significance of this monitoring will be explained below.

Using a configuration in which a single sealing device is positioned below the jetting device, perforation and treatment of precise locations along a vertical or deviated wellbore may be accomplished by incorporation of a depth locating device within the assembly. Notably, a mechanical casing collar locator permits precise setting of the sealing device in advance of perforation, and maintains the position of the assembly during perforation and treatment. This location ability, particularly in combination with coiled tubing deployment, overcomes positional difficulties commonly encountered with other perforation and treatment systems.

The sealing device therefore serves to maintain the position of the tool assembly downhole, and ensure the perforated wellbore is hydraulically isolated from the previously treated portion of the wellbore below. The sealing device shown in the drawings is a mechanically actuated resettable packer. Other suitable sealing devices may be used in substitution.

When the sealing device is set against the casing prior to perforation, this may assist in maintaining the position and orientation of the tool string during perforation and treatment of the wellbore. Alternatively, the sealing assembly may be actuated following perforation. In either case, the sealing assembly is set against the casing beneath the perforated interval of interest, to hydraulically isolate the lower wellbore (which may have been previously perforated and treated) from the interval to be treated. That is, the seal defines the lower limit of the wellbore interval to be treated. Typically, this lower limit will be downhole of the most recently formed perforations, but uphole of previously treated perforations. Such configuration will enable treatment fluid to be delivered to the most recently formed perforations by application of said treatment fluid to the wellbore annulus 182 from surface.

As shown in FIG. 10, the sealing assembly 130 is mechanically actuated, including a compressible packing element 131 for providing a hydraulic seal between the tool string and casing when actuated, and slips 132 for engaging the casing to set the compressible packing element 131. In the embodiment shown in FIGS. 10 through 11C, the mechanism for setting the sealing assembly involves a stationary pin 133 sliding within a J profile 134 formed about the sealing assembly mandrel 135. The pin 133 is held in place against the bottom sub mandrel by a two-piece clutch ring 136, and the bottom sub mandrel 150 slides over the sealing assembly mandrel 135, which bears the J profile. The clutch ring has debris relief openings 137 for allowing passage of fluid and solids during sliding of the pin 133 within the J profile 134.

Various J profiles suitable for actuating mechanical set packers and other downhole tools are known within the art. One suitable J profile 134 is shown in FIG. 11B, having three sequential positions that are repeated about the mandrel. Debris relief apertures 138 are present at various locations within the J-profile to permit discharge of settled solids as the pin 133 slides within the J profile. The J slots 134 are also deeper than would generally be required based on the pin length alone, which further provides accommodation for debris accumulation and relief without inhibiting actuation of the sealing device.

With reference to the J profile shown in FIG. 11B, three pin stop positions are shown, namely a compression set position 139 a, a seal release position 139 b, and a running-in position 139 c. The sealing assembly mandrel 135 is coupled to the pull tube 149, which is slidable with respect to the bottom sub mandrel 150 that holds the pin 133. The bottom sub mandrel 150 also bears mechanical slips for engaging the casing to provide resistance against sliding movement of the sealing assembly mandrel 135, such that the pin 133 slides within the J profile 134 as the pull tube (and sealing assembly mandrel) is manipulated from surface.

Equalization Valve

In order to equalize pressure across the sealing device and permit unsetting of the compressible packing element under various circumstances, an equalization valve 140 is present within the tool assembly. While prior devices may include a valve for equalizing pressure across the packer, such equalization is typically enabled in one direction only, for example from the wellbore segment below the sealing device to the wellbore annulus above the sealing device. The presently described equalization valve permits constant fluid communication between the tubing string and wellbore annulus, and, when the valve is in fully open position, also with the portion of the wellbore beneath the sealing device. Moreover, fluid and solids may pass in forward or reverse direction between these three compartments. Accordingly, appropriate manipulation of these circulation pathways allows flushing of the assembly, preventing settling of solids against or within the assembly. Should a blockage occur, further manipulation of the assembly and appropriate fluid selection will allow forward or reverse circulation to the perforations to clear the blockage.

As shown in FIG. 8, the present equalization valve is operated by sliding movement of an equalization plug 141 within a valve housing 145 (FIGS. 9A and 9B). Such slidable movement is actuated from surface by pulling or pushing on the coiled tubing, which is anchored to the assembly by a main pull tube 149. The main pull tube is generally cylindrical and contains a ball and seat valve to prevent backflow of fluids through from the equalization valve to the tubing string during application of fluid through the jet nozzles (located upstream of the pull tube). The equalization plug 141 is anchored over the pull tube 149, forming an upper shoulder 141 a that limits the extent of travel of the equalization plug 141 within the valve housing 145. Specifically, an upper lock nut 143 is attached to the valve housing 145 and seals against the outer surface of the pull tube 149, defining a stop 143 a for abutment against the upper shoulder 141 a of the equalization plug.

The lower end of the valve housing 145 is anchored over assembly mandrel 160, defining a lowermost limit to which the equalization plug 141 may travel within the valve housing 145. It should be noted that the equalization plug bears a hollow cylindrical core that extends from the upper end of the equalization plug 141 to the inner ports 142. That is, the equalization plug 141 is closed at its lower end beneath the inner ports, forming a profiled solid cylindrical plug 144 a overlaid with a bonded seal 144 b. The solid plug end 144 a and bonded seal 144 b are sized to engage the inner diameter of the lower tool mandrel 160, preventing fluid communication between wellbore annulus/tubing string and the lower wellbore when the equalization plug 141 has reached the lower limit of travel and the sealing device (downhole of the equalization valve) is set against the casing.

The engagement of the bonded seal 144 b within the mandrel 160 is sufficient to prevent fluid passage, but may be removed to open the mandrel by applying sufficient pull force to the coiled tubing. This pull force is less than the pull force required to unset the sealing device, as will be discussed below. Accordingly, the equalization valve may be opened by application of pulling force to the tubing string while the sealing device remains set against the wellbore casing.

With respect to debris relief, when the sealing device is set against the wellbore casing with the equalization plug 141 in the sealed, or lowermost, position, the inner ports 142 and outer ports 146 are aligned. This alignment provides two potential circulation flowpaths from surface to the perforations, which may be manipulated from surface as will be described. That is, fluid may be circulated to the perforations by flushing the wellbore annulus alone. During this flushing, a sufficient fluid volume is also delivered through the tubing string to maintain the ball valve within the pull tube in seated position, to prevent collapse of the tubing, and to prevent clogging of the jet nozzles.

Should reverse circulation be required, fluid delivery down the tubing string is terminated, while delivery of fluid to the wellbore annulus continues. As the jet nozzles are of insufficient diameter to receive significant amounts of fluid from the annulus, fluid will instead circulate through the aligned equalization ports, unseating the ball within the pull tube, and thereby providing a return fluid flowpath to surface through the tubing string. Accordingly, the wellbore annulus may be flushed by forward or reverse circulation when the sealing device is actuated and the equalization plug is in the lowermost position.

When the sealing device is to be released (after flushing of the annulus, if necessary to remove solids or other debris), a pulling force is applied to the tubing string to unseat the cylindrical plug 144 a and bonded seal 144 b from within the lower mandrel 160. This will allow equalization of pressure beneath and above the seal, allowing it to be unset and moved up-hole to the next interval.

Components may be duplicated within the assembly, and spaced apart as desired, for example by connecting one or more blast joints within the assembly. This spacing may be used to protect the tool assembly components from abrasive damage downhole, such as when solids are expelled from the perforations following pressurized treatment. For example, the perforating device may be spaced above the equalizing valve and sealing device using blast joints such that the blast joints receive the initial abrasive fluid expelled from the perforations as treatment is terminated and the tool is pulled uphole.

The equalization valve therefore serves as a multi-function valve, and may be incorporated into various types of downhole assemblies, and manipulated to effect various functions, as required. That is, the equalization valve may be placed within any tubing-deployed assembly and positioned within the assembly to provide selective reverse circulation capability, and to aid in equalizing pressures between wellbore annulus segments, and with the tubing string flowpath to surface. When the equalization plug is in the sealed, or lowermost position, forward or reverse circulation may be effected by manipulation of fluids applied to the tubing string and/or wellbore annulus from surface. The equalization plug may be unset from the sealed position to allow fluid flow to/from the lower tool mandrel, continuous with the tubing string upon which the assembly is deployed. When the equalization plug is associated with a sealing device, this action will allow pressure equalization across the sealing device.

Notably, using the presently described valve and suitable variants, fluid may be circulated through the valve housing when the equalization valve is in any position, providing constant flow through the valve housing to prevent clogging with debris. Accordingly, the equalization valve may be particularly useful when incorporated into downhole assemblies deployed in sand-laden environments.

It is noted that the presently described equalization plug may be machined to any suitable configuration that will provide a valve stem for seating within the lower assembly mandrel, and which is actuable from surface without impeding flow from the outer ports 146 of the valve housing 145 to the ball valve. By similar logic, the ball valve may be replaced with any suitable check valve/one-way valve.

In the embodiment shown in the drawings, it is advantageous that the pull tube actuates both the equalization plug and the J mechanism, at varying forces to allow selective actuation. However, other mechanisms for providing this functionality may now be apparent to those skilled in this art field and are within the scope of the present teaching.

Further Debris Relief Features

The present J profile bears debris relief apertures 138 to allow clearance of solid particles from the J slot that may otherwise complicate setting and unsetting of the packer. The relative proportions of the pin and slot include sufficient clearance (for example 1/16 or ⅛-inch clearance) in both depth and width to permit sliding of pin in the slot when a certain amount of debris is present, enabling the sand to be driven along the slot and through the apertures 138 by the pin during actuation of the packer by application of force from surface. The number and shape of the apertures may vary depending on the environment in which the tool is used. For example, if a significant amount of debris is expected to contact the J slot, the slot may instead include a narrow opening along the entire base of the slot to allow continuous debris movement through the J slot.

A mechanical casing collar locator (MCCL) is incorporated into the particular tool string that is shown in the Figures. When this type of locating device is present within a tool string, the fingers 161 of the locator are typically biased outwardly so as to slide against the casing as the assembly is moved within the wellbore. As shown in FIG. 12, the MCCL mandrel 160 of the present assembly includes fingers 161 that are biased (for example using resilient element 162) outwardly so as to engage the casing as the assembly is moved along the wellbore. As shown, each finger 161 is held within a cavity against the resilient element 162 by a retention sleeve 164 threaded over the MCCL mandrel 160. A narrow slot 163 extends longitudinally within each cavity over which the resilient element is placed, to allow fluid communication between the cavity and the tubing string. Further, another slot within the outer surface of the mandrel extends across each cavity such that fluid may enter each cavity from the wellbore annulus. Once assembled, a fluid flowpath extends between the wellbore annulus 182, to the cavity beneath each finger 161, and through the cavity to the tubing string. Accordingly, this permits flushing of fluid past the fingers during operation. This open design minimizes the risk of debris accumulation adjacent the resilient element, which may force the fingers to remain extended against the casing or within a casing joint.

Detection of Adverse Events

During the application of treatment to the perforations via the wellbore annulus, the formation may stop taking up fluid, and the sand suspended within the fracturing fluid may settle within the fracture, at the perforation, on the packer, and/or against the tool assembly. As further circulation of proppant-laden fluid down the annulus will cause further undesirable solids accumulation, early notification of such an event is important for successful clearing of the annulus and, ultimately, removal of the tool string from the wellbore.

During treatment of the perforations down the wellbore annulus using the tool string shown in the Figures, fluid will typically be delivered down the tubing string at a constant (minimal) rate to maintain pressure within the tubing string and keep the jet nozzles clear. The pressure required to maintain this fluid delivery may be monitored from surface. The pressure during delivery of treatment fluid to the perforations via the wellbore annulus is likewise monitored. Accordingly, the tubing string may be used as a “dead leg” to accurately calculate (estimate/determine) the fracture extension pressure by eliminating the pressure that is otherwise lost to friction during treatment applied to the wellbore. By understanding the fracture extension pressure trend (also referred to as stimulation extension pressure), early detection of solids accumulation at the perforations is possible. That is, the operator will quickly recognize a failure of the formation to take up further treatment fluid by comparing the pressure trend during delivery of treatment fluid down the wellbore annulus with the pressure trend during delivery of fluid down the tubing string. Early recognition of an inconsistency will allow early intervention to prevent debris accumulation at the perforations and about the tool.

During treatment, a desired volume of fluid is delivered to the formation through the most recently perforated interval, while the remainder of the wellbore below the interval (which may have been previously perforated and treated) is hydraulically isolated from the treatment interval. Should the treatment be successfully delivered down the annulus successfully, the sealing device may be unset by pulling the equalization plug from the lower mandrel. This will equalize pressure between the wellbore annulus and the wellbore beneath the seal. Further pulling force on the tubing string will unset the packer by sliding of the pin 133 to the unset position 139 b in the J profile. The assembly may then be moved uphole to perforate and treat another interval.

However, should treatment monitoring suggest that fluid is not being successfully delivered, indicating that solids may be settling within the annulus, various steps may be taken to clear the settled solids from the annulus. For example, pumping rate, viscosity, or composition of the annulus treatment fluid may be altered to circulate solids to surface.

Should the above clearing methods be unsuccessful in correcting the situation (for example if the interval of interest is located a great distance downhole that prevents sufficient circulation rates/pressures at the perforations to clear solids), the operator may initiate a reverse circulation cycle as described above. That is, flow downhole through the tubing string may be terminated to allow annulus fluid to enter the tool string through the equalization ports, unseating the ball valve and allowing upward flow through the tubing string to surface. During such reverse circulation, the equalizer valve remains closed to the annulus beneath the sealing assembly.

Method

A method for deploying and using the above-described tool assembly, and similar functioning tool assemblies, is provided. The method includes at least the following steps, which may be performed in any logical order based on the particular configuration of tool assembly used: running a tool string downhole to a predetermined depth, the tool string including a hydra-jet perforating assembly and a packer assembly below the perforating assembly setting the packer assembly against the wellbore casing creating perforations in the casing by jetting fluid from nozzles within the perforating assembly pumping a treatment fluid down the wellbore annulus from surface under pressure, while simultaneously pumping fluid down the tubing string and through the jet nozzles; and monitoring fracture extension pressure during treatment.

In addition, any or all of the following additional steps may be performed: reverse circulating annulus fluid to surface through the tubing string equalizing pressure above and below the sealing device equalizing pressure between the tubing string and wellbore annulus without unseating same from the casing unseating the sealing assembly from the casing repeating any or all of the above steps within the same wellbore interval moving the tool string to another predetermined interval within the same wellbore and repeating any or all of the above steps

A method of providing a reverse circulation pathway within a downhole assembly is described. This method is particularly useful in sand-laden environments, where debris accumulation may require alternate circulation flowpaths. With reference to FIGS. 8, 9A, and 9B, an equalization valve 140 is provided, associated with a ball and seat valve or similar device for diverting fluid from the tubing string during normal operation of the assembly, i.e. when reverse circulation is not required. That is, delivery of fluid to the tubing string from surface will force the ball into its seat, and prevent direct fluid communication from the tubing string to the equalization valve. The equalization valve is, however, in indirect fluid communication with the tubing string, as fluid diverted from the tubing string into the wellbore annulus flows through outer ports 146 of the valve housing to bathe/flush the equalization plug 141 and inner surfaces of the valve housing 145. As the equalization plug 141 also includes inner ports 142, fluid may flow through outer ports 146 and inner ports 142, whether or not said ports are aligned. Accordingly, the equalization valve is continually washed with wellbore annulus fluid, assisting circulation downhole and preventing settling or accumulation of solids against the tool or within the valve.

Typically, the equalization plug will be slidable within the valve housing between a sealed position—in which the cylindrical plug 144 a and bonded seal 144 b are engaged within the lower mandrel, with inner and outer ports 142, 146 aligned as discussed above—and an unsealed position. The plug is operatively attached to a pull tube 149, which may be actuated from surface to control the position of the equalization plug 141 within the valve housing 145.

Should a blockage occur downhole, for example above a sealing device within the assembly, delivery of fluid through the tubing string at rates and pressures sufficient to clear the blockage may not be possible, and likewise, delivery of clear fluid to the wellbore annulus may not dislodge the debris. Accordingly, in such situations, reverse circulation may be effected while the inner and outer ports remain aligned, simply by manipulating the type and rate of fluid delivered to the tubing string and wellbore annulus from surface. Where the hydraulic pressure within the wellbore annulus exceeds the hydraulic pressure down the tubing string (for example when fluid delivery to the tubing string ceases), fluid within the equalization valve will force the ball to unseat, providing reverse circulation to surface through the tubing string, carrying flowable solids.

Further, the plug may be removed from the lower mandrel by application of force to the pull tube (by pulling on the tubing string from surface). In this unseated position, a further flowpath is opened from the lower tool mandrel to the inner valve housing (and thereby to the tubing string and wellbore annulus). Where a sealing device is present beneath the equalization device, pressure across the sealing device will be equalized allowing unsetting of the sealing device.

It should be noted that the fluid flowpath from outer ports 146 to the tubing string is available in any position of the equalization plug. That is, this flowpath is only blocked when the ball is set within the seat based on fluid down tubing string. When the equalization plug is in its lowermost position, the inner and outer ports are aligned to permit flow into and out of the equalization valve, but fluid cannot pass down through the lower assembly mandrel. When the equalization plug is in the unsealed position, the inner and outer ports are not aligned, but fluid may still pass through each set of ports, into and out of the equalization valve. Fluid may also pass to and from the lower assembly mandrel. In either position, when the pressure beneath the ball valve is sufficient to unseat the ball, fluid may also flow upward through the tubing string.

The above-described embodiments of the present invention are intended to be examples only. Each of the features, elements, and steps of the above-described embodiments may be combined in any suitable manner in accordance with the general spirit of the teachings provided herein. Alterations, modifications and variations may be effected by those of skill in the art without departing from the scope of the invention, which is defined solely by the claims appended hereto.

The foregoing presents a particular embodiment of a system embodying the principles of the invention. Those skilled in the art will be able to devise alternatives and variations which, even if not explicitly disclosed herein, embody those principles and are thus within the invention's spirit and scope. Although particular embodiments of the present invention have been shown and described, they are not intended to limit what this patent covers. One skilled in the art will understand that various changes and modifications may be made without departing from the scope of the present invention as literally and equivalently covered by the following claims. 

What is claimed is:
 1. An assembly for treating an interval of a wellbore, comprising: a resettable sealing device deployed on a tubing string, the sealing device including a J-profile with a pin slidably-disposed in said J-profile for actuating the sealing device, wherein the J-profile comprises one or more debris discharge ports through the J-profile to permit discharge of debris upon sliding movement of the pin within the J-profile.
 2. The assembly recited in claim 1, further comprising a locator having outwardly biased locating members configured to slide against a cased wellbore to verify a downhole location of the assembly prior to actuation of the resettable sealing device.
 3. The assembly recited in claim 2, wherein the locator comprises a cavity beneath the outwardly biased locating members configured to allow the passage of fluid and debris through the locator to the tubing string.
 4. The assembly recited in claim 1, wherein the pin is actuated along the J-profile by application of mechanical force to the tubing string.
 5. The assembly recited in claim 1, wherein the J-profile has a width that is at least 1/16 inch greater than a diameter of the pin to allow debris movement within the J-profile without impeding travel of the pin along the J-profile.
 6. The assembly recited in claim 1, wherein the J-profile has a depth that is at least 1/16 inch greater than a length of the pin to allow debris movement within the J-profile without impeding travel of the pin along the J-profile.
 7. The assembly recited in claim 1, wherein the J-profile has a width that is at least 1/16 inch greater than a diameter of the pin and a depth that is at least 1/16 inch greater than a length of the pin to allow debris movement within the J-profile without impeding travel of the pin along the J-profile.
 8. The assembly recited in claim 1, wherein the resettable sealing device is a mechanical set packer.
 9. An assembly for treating an interval of a wellbore, comprising: a resettable sealing device deployed on a tubing string, the sealing device including a J-profile with a pin slidably-disposed in said J-profile for actuating the sealing device wherein the pin is held to the assembly by a clutch ring, and wherein the clutch ring comprises an aperture to permit discharge of the debris from about the pin while the pin slides within the J-profile.
 10. An assembly for treating an interval of a wellbore, comprising: a resettable sealing device deployed on a tubing string, the sealing device including a J-profile with a pin slidably disposed in said J-profile for actuating the sealing device; an equalization valve for actuating slidable movement of the sliding pin within the resettable sealing device wherein the equalization valve comprises an equalization valve plug slidably disposed within an equalization valve housing continuous with the resettable sealing device for actuating slidable movement of the pin within the J-profile, wherein the J-profile comprises one or more debris discharge ports through the J-profile to permit discharge of debris upon sliding movement of the pin within the J-profile.
 11. The assembly recited in claim 10, wherein the equalization plug is slidably actuated by application of mechanical force to the tubing string to set or unset the resettable sealing device within the wellbore.
 12. The assembly recited in claim 10, wherein the equalization valve comprises at least one inner port providing fluid communication between a central, axial bore within the equalization valve plug and an outer surface of the equalization valve plug and at least one outer port in the equalization valve housing.
 13. The assembly recited in claim 12, wherein the at least one inner port and the at least one outer port are substantially co-planar when the equalization valve is in a closed position.
 14. A method for the treatment of a formation intersected by a cased wellbore, the method comprising the steps of: providing a tool assembly comprising a sealing device comprising a J-profile with a pin for use in actuating the sealing device; deploying the tool assembly on a tubing string within the cased wellbore; setting the sealing device against the cased wellbore; while the sealing device remains set against the cased wellbore, circulating treatment fluid down an annulus formed by the cased wellbore to treat the formation through one or more openings in the casing of the cased wellbore; \ circulating the treatment fluid from the annulus; reverse circulating the treatment fluid from the annulus to surface through the tubing string; and unsetting the sealing device from the cased wellbore, wherein the J-profile comprises one or more debris discharge ports through the J-profile to permit discharge of debris upon sliding movement of the pin within the J-profile.
 15. The method recited in claim 14, wherein the sealing device remains set against the cased wellbore during reverse circulation.
 16. The method recited in claim 14, wherein the treatment fluid comprises flowable solids, and wherein the flowable solids are circulated through the J-profile.
 17. A method for treatment of a formation intersected by a cased wellbore, the method comprising the steps of: providing a tool assembly comprising a sealing device comprising a J-profile with a pin for use in actuating the sealing device; deploying the tool assembly on a tubing string within the cased wellbore; setting the sealing device against the cased wellbore; while the sealing device is set against the cased wellbore, circulating treatment fluid down an annulus between the cased wellbore and the tool assembly to treat the formation through one or more openings in the casing of the cased wellbore; opening an equalization passage extending through the sealing device to permit fluid communication of a first portion of the annulus beneath the sealing device to a second portion of the annulus above the sealing device; and, unsetting the sealing device from the cased wellbore, wherein the J-profile comprises one or more debris discharge ports through the J-profile to permit discharge of debris upon sliding movement of the pin within the J-profile.
 18. A pin carrier configured for use with a J-profile of a downhole tool comprising: a generally annular body having an upper surface, a lower surface, a generally cylindrical outer surface, and a generally cylindrical inner surface; at least one passageway extending from the upper surface to the lower surface of the annular body and sized to allow the passage of fluid and debris through the pin carrier.
 19. The pin carrier recited in claim 18 wherein the at least one passageway extending from the upper surface to the lower surface of the annular body is a cutout in the generally cylindrical inner surface of the generally annular body.
 20. The pin carrier recited in claim 19 wherein the cutout in the generally cylindrical inner surface of the generally annular body has a semi-circular transverse cross section.
 21. The pin carrier recited in claim 18 wherein the generally annular body is a two-piece body wherein each piece of the two-piece body has a substantially semi-circular transverse cross section. 